Final answer:
The prominent muscular ridges inside the right atrium and right auricle are the pectinate muscles, which are distinct from structures like chordae tendineae and trabeculae carneae found in the ventricles; the correct option is D) pectinate muscles.
Step-by-step explanation:
The features described as prominent muscular ridges that extend along the inner surface of the right auricle and across the adjacent anterior wall of the right atrium are known as the pectinate muscles. These ridges are unique to the right atrium and are present in the right auricle, but notably absent in the left atrium except in the auricle.
The pectinate muscles contrast with other structures such as the chordae tendineae which connect the flaps of the heart valves to the papillary muscles in the ventricles, and the trabeculae carneae which are ridges of muscle covered by endocardium found in the ventricles.
Therefore, the correct option is D) pectinate muscles.